Grain drier



OC- 27, 1953 B. ToMLlNsoN ET AL GRAIN DRIER Filed sept,` 4, 1951Patented Oct. 27, 1953 GRAIN DRIER Ben L. Tomlinson,

E. Carlson,

St. Louis Park, and Donald Litchfield, Minn., assignors to Arid AireManufacturing Company,

St. Louis Park,

Minn., a corporation of Minnesota Application September 4, 1951, SerialNo. 244,972

This invention relates to dryers and dehydrators for drying grain andother products. More particularly, it relates to grain dryers of thetype wherein a source of relatively hot air is utilized to dry the grainduring its continuous passage through the dryer.

This invention constitutes improvements over the invention as disclosedand claimed in U. S'. Letters Patent No. 2,490,176, dated December 6,1949, and entitled Grain Drier, nled by William E. Tomlinson and Ben L.Tomlinson on September 5, 1947. l

Although the invention disclosed and claimed in the patent referred toin the preceding paragraph provides a grain dryer of high operatingefciency, we have found that by making certain improvements thereto itis possible to increase the efficiency of the drying unit andpractically eliminate fire hazards normally attendant therewith.

It is a general object of our invention to provide a novel and improvedgrain dryer of simple and improved construction and having increasedefficiency, compactability and safety during operation.

A more specific object is to provide an improved grain dryer constructedto distribute the hot air relatively uniformly throughout the length ofthe drying chamber to accomplish more uniform and effective drying orthe grain passing therethrough.

Another object is to provide an improved grain dryer constructed toeffectively and continuously remove the dust and dirt which normallycollects Within the interior of a grain dryer and thereby substantiallyreduce the danger of re resulting therefrom.

Another object is to provide an improved grain dryer constructed toprevent substantially allof the hot air, when released within the dryingchamber, from rising and passing through only the portions of theconveyor which are immediately adjacent the discharge of such hot air tothe neglect of the portions of the conveyor more removed.

Another object is to provide an improved grain dryer constructed toeffectively collect along a central area the dust and dirt which Worksits way through the grain and the conveyor and to thereafter eflicientlyremove the same.

6 Claims. (Cl. 263-8) Another object is to provide a grain dryer havinginherent means for retaining a substantial portion of the hot airbeneath a retaining hood-to release the same at points substantiallyremoved from the discharge area. i Y i Another object is to provide anovel and improved grain dryer having improved structure foraccomplishing complete and thorough mixing of the hot air discharged bythe burner with cool air prior to its release within the drying chamberof the dryer.

These and other objects and advantages of my invention will be moreapparent from the following description made in connection with theaccompanying drawings, wherein like reference characters refer tosimilar parts throughout the several views and in which Fig. l is aperspective view of one embodiment of our invention with portions of thewalls broken away to reveal the interior thereof;

Fig. 2 is a vertical sectional view taken longitudinally of the dryer.

Fig. 3 is a transverse vertical sectional view taken along approximatelyline 3-3 of Fig. 2.

Fig. 4 is a perspective view of the tubular member utilized to effect amore thorough mixing of the hot and cool air adjacent the burner.

One embodiment of our invention may include as shown in Figs. 1-4, anelongated housing indicated generally as and having sidewalls 1, a topwall e, a receiving end SA, and a delivery end 6B. The walls of thehousing 6 are insulated to prevent the escape of hot air therefrom andthe interior of the housing is divided by a partition 9 into a hotchamber I0 and a cooling chamber ll. The hot chamber I0 has a generallyV- shaped bottom I2 while the cooling chamber II has a generallyinverted V-shaped bottom I3. The cooling chamber II communicates withthe exterior by means of a louvered cooling air intake i4 arrangedadjacent the lower portion of the housing and within the opposite sidewalls thereof as best shown in Fig. 1. Secured to the top wall -8 of thehousing within the hot chamber l0 is a drying blower I5 which is drivenby a motor I6. Also secured to the top wall 8 of the housing within thecooling chamber I I is a cooling blower I1 driven by a motor I8.

Mounted within the interior of the housing to extend longitudinallythereof throughout the major portion of its length and medially disposedrelative to the height of the housing is an endless porous conveyor I9.This porous conveyor I 9 is formed of material which will readily permitair to pass therethrough but the openings thereof'are sufficiently smallto prevent small grains from Working downwardly therethrough. It hasbeen found that a type of wire mesh belting is best adapted for thistype of conveyor. As shown, the conveyor is provided with a rearalignment sprocket 20 and With-a main drive sprocket 2| 'whichpositively drives the endless conveyor continuously around its mounting.The conveyor is provided with a plurality of apron support rollers 22 tofacilitate its movement throughout the length of the housing.

The conveyor is driven by means of a drive chain 23 which is connectedwith a speed reducer 24 which in turn is driven by al variable speeddrive motor 25. Rakes or agitator bars 26 are mounted between theopposite side walls ofmthe housing directly above the conveyor I9 thatwarm air may readilypasslaterally therebetween 'to rise .upwardlythrough the 'conveyor I9. A portion of the hot air will be coniinedwithin the confines of the hood and driven longitudinally thereof to bedischarged beyond the Wend 'of the hood adjacent the receiving end ofwill drag along the upper Vsurface of the grain j being dried.

At the receiving end 6a of the housing ll there is provided a wet grainintake spout which empties into the intake hoppe`3l. The intake spoutand the hopper act as a conduit for the incoming wet grain and the flowtherethrough is controlled by a control gate 32. The control gate 32 maybe regulated by an adjustment handle 33. K l A At the delivery end Gb ofthe housing andat Vthe 'delivery end of the conveyor I9 and slightlytherebelow is positioned a hopper 3.4l which extends transversely of thehousing. The floor of this hopper 34 is disposed at an angle so that thegrain which has been dried` and discharged over the adjacent end of theconveyor will drop into the hopper and slide' to its lowest point Withinwhich a dry grain discharge lscrew conveyor 35 is mounted for rotationon a horizontal axis. This screw conveyor 35 discharges into Yadischarge spout 36 and is driven by a second drive sprocket 31 vwhich isconnected as shown to `the variable speed drive motor 25.

Y Mounted fn the Ulower portion 'of the h'using 6 adjacent Vits deliveryend v6b is a blast type oil burner indicated generally as 38 which has adischarge 39 which terminates beneath the inverted V-shaped bottom I3Aof the Cooling chamber II. The discharge end -3'9 'is surfrounde'd'by atubular member 40 which tapers throughout its length toward thereceiving end of the housing. VThe larger end of the tubular member isdisposed so that the discharge 39 oi the burner extends well within theinterior oi the 'tubular 'member 4b. The smaller end '4| of 'the tubularmember `extends through the partition 9 and into the interior of the hotchamber lll as best shown in Fig. 2.A This tubular member 4o has fa.pal'rjef ports 42 formedtherethrough vand 'disposed directly oppositethe discharge 379 of the burner.

These ports cause the interior of the tubular member 40 to communicateterior of that member to therethrough. A supply of cold air is'available through the screening 43 which is disposed at the neuemr ofme housing directly 'below elle discharge of the burner. Thus cool v:airis Spermitted to rise through "this screen and enterthe larger end ofthe tubular member 40has well as the ports 42 to mix with the extremelyhot air discharged at 39 by the burner-38. A n

l Mounted within the interior of thehot chamber I0 and extendinglongitudinally thereof beneath the conveyor I9 but at a level above thedischarge of hot air through Vthe smaller end 4l of the tubular member4o is a :heed or air distributor 44. As best shown Fig. 3 this `hood ismounted upon a plurality `of upstanding arms 45 which extend upwardlyfromthe V-shaped bottom I'2 of the hot chamber l0. This hood 44 Vispreferably of an inverted V-shapewhe'n viewed cross-sectionally., asshown inFig. @Land extends a substantial distance through the length ofthe hot chamber Il), preier'ably vto a beyond the middle thereof. Thesides of the hood A44 are spaced from the side walls `of the housing andfrom the walls 5 forming the bottom l2 so with the area 'ex- `permit airtc pass the housing;

The v-shepeu bottom ef' me not chamber lo fis provided with an augertype clean-outcon- 'veyol'` 46 which extends longitudinally of thecooling chamber and the housing. This is best shown vin Figs. '2 and 3.This conveyor 46 is rotatably mounted and driven by the clean-out augerdrive 41 which is connected to the variable speed drive motor v25 by apulley 48 and a belt 49. This screw type conveyor discharges at thereceiving end of the housing to the exterior of the housing as at 50. l

The controls for the entire unit are mounted adjacent the delivery endof the housing. vThese controls are not considered to be part of theinvention but they will be briefly enumerated and identiiied herein yforthe purpose of clarity. In conjunction with the oil burner I0, there isAprovided a manual -oi'l valve 5I, an oil filter 52, an oil pressureregulator 53, an oil pump 5,4, a solenoid oil valve 55 and an oil burnercontrol motor v56. Also provided is a low limit control 51, a .highlimit lcontrol and thermometer 58 and a vaporstat 59. A foot .switch B,an electric control panel BI, an electric eye '62 and a lc'o'n't'rl'll63 for the electric eye complete the controls.

Operation-s In operation the conveyor `ISI is nrst started. Thecombustion blower then starts and Opens the solenoid valve whichcontrols the oil feed. This oil feed is connected in series with thevalve and the valve is opened only when at full pressure to preventsmoking and/or improper fuel and air mixture. The oil is under pressureapproximating l0 pounds and is forced through the spray nozzle of theburner for combustion. Air comes around the nozzle from the rear toprovide the oxygen for combustion.

rllhe electric eye, in case the lire of the burner goes out, iselectrically connected to cut oi all of the mechanisms within thevburner and to automatically sound a warning horn. The low limit controldoes the same when the temperature within the chamber above the materialbeing dried reaches a level above 160 `degrees Fahrenheit and the high-limit control does the same if the temperature in the hot air chambershould nreach a level above 260 degrees Fahrenheit.

rIhe grain is fed into the wet grain intake spout -30 Afrom the sourceof grain to be dried. This grain passes into the hopper 3 I, through thegate 32 and is deposited thereby upon the receiving end Aof the conveyorI9 in `an even stratum. As .the endless conveyor I9 `moves around vitsmounting, the stratum of grain .21 passes slowly toward the deliveryYend V6b of the housing at a steady rate. As it .passes through ktherakes 2.6 the grain is slightly agitated and disturbed to `facilitatethe ypassing of the hot air upwardly therethrough. The blower I5 drawsthe hot air upwardly through the stratum of grain and discharges it byitstangential discharge to the exterior of the housing. Y

y By the time the grain has reached the panel 9 to pass beneath the flap29 it has been substantially dried but is at a temperature too high forstorage. The blower I1, however, draws cool air upwardly through the'cooling chamber and through the stratum of warm grain to cool the samewhile it is within the cooling chamber. This cool air, which of coursewill be warmed by the grain, is discharged to the exterior of thehousing. The cooled grain is thereafter discharged i over the end of theconveyor i9 into the hopper 34 and passes downwardly into the dry graindischarge auger 35 which in turn carries the same laterally of thehousing and `into the discharge spout 36.

As the grain passes through the hot chamber dust, dirt and other foreignmaterials, ordinarily found mixed with grain which has not been cleaned,will gradually work downwardly through the stratum of grain and throughthe porous conv Veyor I9. This downward progression of foreign`substantial fire hazard. `The continuous elimination of this dirt anddust and its discharge to a point exterior of the housing eliminatesthis fire hazard.

The hot air which is discharged by the burner 33 is at such a hightemperature that cool air is mixed therewith prior to its releasebeneath the conveyor for drying purposes to prevent injury to the grain.This is accomplished through the use of the tubular member 40 whichpermits cool air to enter its larger end in surrounding relation to thedischarge 39 of the burner. -The arrows in Fig. 2 indicate the directionof flow of such cool air. We have found, however, that it is importantthat means be provided for uniformly mixing this cool air with the hotair discharged by the burner. have tapered the tubular member 40 tofacilitate the mixing of the warm and hot air. In addition we have foundit to be advantageous to provide a pair of ports 42 positioned as shownso that additional cool air will be drawn therethrough to mix with thehot air discharged from the burner at 39. The introduction of cool airfrom this lateral point of vantage and having a cross-directionalmovement induces or creates a vorticity within the interior of thetubular member 4i) which substantially increases the mixing action ofthe warm and cool air. Thus by the time the hot air has reached thedischarge 4| of the tubular member 4G, it has been thoroughly mixed soas to have an even temperature throughout its mass.

The hot air discharged by the tubular mem'ber 40 is released at a pointbeneath the hood 44 as best shown in Fig. 2. This hot air of coursetends to rise immediately upon its release. We have found however thatif such rising action is permitted uninhibited, uneven drying may resultwithin the stratum of grain at its passes along with the conveyor.` Inother Words, we have found that a greater eiiiciency may be obtained bydistributing the discharge of hot air over a major portion of the hotchamber lil so that the hot air will be released more uniformlythroughout the various points of the hot chamber. The inverted V-shapedhood 44 permits a substantial To accomplish this, we

` portion of this hot air to move laterally and upwardly between itssides and the bottom l2 to dry the grain immediately thereabove. At thesame time, a substantial portion of the hot air remains within the conneof the hood and is driven longitudinally of the housing and of the hoodto be released adjacent the end of the hood which is adjacent thereceiving end of the housing. Thus it can be readily seen that arelatively uniform distribution of the hot air is provided so that thegrain deposited upon the conveyor will be dried substantially equally asrapidly adjacent the receiving end as it will adjacent the partition 9.We have found that such a hood produces a substantially uniformdistribution of the hot air within the hot chamber I0 and effects asubstantially more uniform drying action.

It should be noted also that by mounting the blowers l5 tnd l1 Withinthe confines of the housing we have substantially increased thecompactability-of the unit. Thus it can be seen that we have provided animproved grain drying unit constructed to effectively and continuouslyremove the dust and dirt which normally collects Within such a unit andwhich normally constitutes a serious iire hazard thereto. At the sametime we have provided structure which substantially increases theeiciency of the unit as a result of accomplishing improved mixing of thehot and cold air and uniform distribution of the mixed air throughoutthe interior of the hot chamber.

It will, of course, be understood that various changes may be made inthe form, `details,.ar rangement and proportions of the various partstwithout departing from the scope of our invenion.

What We hereby claim is:

l. A continuous grain dryer having in combination a housing having `adelivery end and a receiving end and a top and a bottom, an endlessporous conveyor extending substantially horizontally throughout themajor portion of the length of said housing and medially disposedrelative to the height thereof, conduit means in the receiving end ofsaid housing adapted when connected to a source of grain to be dried todeliver continuously a stratum of such grain upon the receiving end ofsaid conveyor, means for delivering dry grain from the delivery end ofsaid housing to a point exterior thereof, a blast type burner mountedWithin said housing adjacent its delivery end and having a hot airdischarge, a transverse partition dividing the interior of said housinginto a larger hot chamber extending from a point inwardly of said burnerto the receiving endof said housing and a cooling chamber extending fromsaid partition to the delivery end of said housing, said cooling chambercommunicating with the exterior at points below said conveyor, saidpartition having an aperture in the central portion thereof foraccommodating said conveyor and the stratum of grain carried thereby,hot air conduit means receiving from the discharge of said burner anddischarging hot air into said hot chamber of said housing `below saidconveyor `and directed longitudinally and centrally of said nemesi ilydistribute the warm iair more uniformly the delivery 'portion Aof lsaidconveyor 'and icirciulated-.in said cooling-chamber.

2. A continuous :grain dryer having ,in combination a lhousing 4'havinga delivery :end and a `.receiving 'end and a top .and a bottom, fan'endless porous conveyor extending substantially horizontally throughoutthe maj or po'rtio'n of the :length `offsaid housing 'and mediall'ydisposed -rel- :ative `to `the .height thereof, :conduit means in v'thereceiving end of said housing adapted when fconncted toa source `o'f:grain rto'be "dried to deliver A'continuously a .stratum of such grainupon the .receiving fend :'of said conveyor, means for Adeliv-er-ing'dry grain from the delivery fend fof fsaid lhousing to a point:exterior thereof,`a blast y-type burner mounted Within said housingadjacent .rits-delivery endandhavn'g a hot air discharge, a transversepartition dividing the 'interior fof vsaid housing vinto "a larger `notchamber extending from apoint inwardiy of fsa-id lburner -tothe-receiving end of said housing .and a cooling cha-'mber extendingfromsaidpartition to the :delivery end of said housing, fsaid coolingchamber `comt.

m-unicating with the exterior :fat Ipoints l below l'said conveyor,saidpartitionhavingan,apertureinthe central portion thereof foraccommodating fsaid conveyor and the stratum V'of 'graincarri'e'dfthereyby .hot .fai-r conduit "means receiving from 'the dis` 1:charge of -sayi'd v:burner .and'ischargingfhotair into -said hotchamberzof said housing below l@said conveyor rand fdirectedSl'ongitu'din'aiiy and .'centrally of :said housing toward the receivingfend `thereof, 'a cleaneout fconveyor .mounted in `the V-lovver yportionl,of said housing lbeiow :said endless porous `v.conveyor and 'extendinglongitudinally thereof in position to receive l-vvhatever dust fand-d-iigt may pass through said ,porous 'conveyorand fall downwardly andto `discharge rtsthnsly iac- Y quired vload exterior-ly Iof saidhousing, rand `an Aex-pelle-r-type blower mounted ,in the upperjportion. Aof said .housing Vabovesa-id :conveyor :and V.having ,anintakeand a discharge communicating @with `:the finterior Aand theexterior foi said .housf,

respectively whereby hot air .and products fof .combustion willYbefd'raWn-eand circulated upward- .,ly through said porous lconveyorand the stratum .of grain l:therein and then discharged from the -dryerand whereby l,cool Vair vv-illuloe` drawn :and circulated upwardlythrough the'delivery portion of said `conveyor and circulated :sa-idfcooling chamber.

. 3. A continuous Ygrain dryer vhaving in com- `lbination :a -housinglhaving Va .delivery en'dzan'd a receiving end and a 'top andLimperforate V-shaped bottom, an' endles's .porous :conveyor :ex-'tendin-gvsubstantially .horizontally thronghotthe :major portion of:the length :of said .fhousinga'nd media-lly disposed relative to theheight ther-eef, conduitmeans in the receiving end of fsa-id .hous- .ingadapted when connected :to fassoiirceV o'f i'grain Ato bedriedwto-deliver continuously 1.a stratumfof such .grain upon thereceiving end `of-.'said1c'on .veyon means for delivering :dry grainfrom the @8 delivery fend fof `=said housing to a point exteriorthereof, :a blast type burner-mounted `withirrsaid housing adjacent itsdelivery-fend and 'fh-airing a .not "air discharge, 'a `transversepartition dividing the interior of said :housing into a larger vhotchamber extending from :a :point inwardly of said burner tto thereceiving end .o`f said `housing and "a cooling 'chamber extending'fromsaid partition to the delivery end of I'said housing, said cooling:chamber 'communicating with the `exterior -at points below saidconveyor, said partition :having Aan apertine inthecentral portionthereo for accommodating said conveyor and the stratumcof grain carriedthereby het air conduit 'meai:ls.r'e iceivn'g :from the discharge yof:said burner :and `idisclrarging .not .lair .into said vfloot chamber-Aof'zisaiid housing below said conveyor and' directed .longi-`tudinally fand centrally yof said housing toward fthe 'receiving fendthereof, a `clean-'out conveyor extending `fl'ongitudfi'nally of said'housing' land A.mounted 'in the .lower .portion thereof' below fsaiidendless porous conveyor and at 'the apex zofsaid 'Veshaped bottomposition to receive whatever dust, dirt and other foreign' materialsWhich/'may pass through lsaidpclirous conveyor :andfalll.dovvnlwardly-and to discharge its ithusly acquired load rexteriorly of-said housing, and an expelientype blower mounted in 'the 'upper portionof said housing above fsaid vconveyoralid .havingan intake and adischargecommunicating*with ther-'interior and the 'exterior Vof saidhousing respectively whereby hot air and products of combustion will bedrawn and :circulated upwardly 'through said porous oonveyorandthefstratumrof .grain 'thereon 'and :then discharged frornfthe dryer'and whereby foo'ol air will be drawn -land circulated upwardly throughthe delivery .portionfof 'said-conveyor and circulated 'inrsaid coolingchamber. f

4. .YA fco'ntinuou's grain "'dry'er having in co'nbinati'on sa housinghaving a delivery Iend and a receiving end anda-Stop and a f'generailyv-snaped bottom when viewed cross-"sectionally, vane'ncl'ess poro'usconveyor extending substantially horizon- 'tallythroufghou't' the majorpor-tion v'of the flength 4of 'said :housing `and rmedialiy disposedrelative .Kto l'the yheight thereof., conduit means inthe receivfin'gvend "'of said iho'usingiadapted lwhen connected to a source for grainYto deliver .continuously a stratum* 'of such grain upon the-receivingiendof :said conveyor, means `for delivering 'gra-in 'from thedelivery end .of said housing r`to ya .point VIe'l'rte'rior thereof, ablast .type `burner mounted lwithin said-fnousingfadjacexrt its deliveryend2end having a hot -air discharge, a transverse partition .dividing:the interior of s'aid'fhousing into :lailrger -hotlcha'inber 'extendingfrom a point inwardly #of :saidbur-ner to the'frece'ivihg'end 'of saidhousing .and a S-coolin-g fchamb'er extending fromzsai'dpartition to thefde'livery end of 1said housing, said fcoolinfg chamber communicatingV'with the fexterior at points below said conveyor, said partitionhaving ian aperture in the eer'itral portion :thereof 'for:accommodating 1Said ,conveyor andthe 'stratum of grain 'carriedthereby, ho't fair fcon'duit :means rec'zeiving from the Adischarge ofsaid burner and discharging hot Pair into said hot fchamberfofisiidhousing fbelow 'said .conveyor Iand Sdirectedwlongiftudmally andcentrally of said housing :toward :the receiving lfend thereof,atpowere'drivn aug-er- 'itype clean-out 'conveyor extendinglongitudinally of said housing and `mounte'dforrotation"about itsAlongi'tuclinal axis `vvithin the :apex 'o'f said V'sh'a'ped 'bottoniand .discharging fexteriorly'f'of 'saidhousin'g Vwhereby dust, .'dirtand-'other foieign materials which pass'through said porous 'con- E@veyor and fall downwardly to constitute fire hazards may be continuouslyand effectively elimi nated and thereby prevented from accumulatingWithin said housing, and an expeller-type blower mounted in the upperportion of said housing above said conveyor and having an intake and adischarge communicating with the interior and the exterior' of saidhousing respectively whereby hot air and products of combustion will bedrawn and circulated upwardly through said poro-us conveyor and thestratum of grain thereon and then discharged from the dryer and wherebycool air will be drawn and circulated upwardly through the deliveryportion of said conveyor and circulate within said cooling chamber.

5. A continuous grain dryer having in combination a housing having adelivery end and a receiving end and a top and a bottom and side walls,an endless porous conveyor extending substantially horizontallythroughout the major portion of the length of said housing and mediallydisposed relative to the height thereof, conduit means in the receivingend of said housing adapted when connected to a source of grain to bedried to deliver continuously a stratum of such grain upon the receivingend of said conveyor, means for delivering dry grain from the deliveryend of said housing to a point exterior thereof, a blast type burnermounted within said housing adjacent its delivery end and having a hotair discharge, a transverse partition dividing the interior of saidhousing into a larger hot chamber extending from a point inwardly ofsaid burner to the receiving end of said housing and a cooling chamberextending from said partition to the delivery end of said housing, saidcooling chamber communicating with the exterior at points below saidconveyor, said partition having an aperture in the central portionthereof for accommodating said conveyor and the stratum of grain carriedthereby hot air conduit means receiving from the discharge of saidburner and discharging hot air into said hot chamber of said housingbelow said conveyor and directed longitudinally and centrally of saidhousing toward the receiving end thereof, an elongated hood membermounted below said conveyor at a level above the discharge of said hotair conduit means and extending from a point adjacent the point ofdischarge of said hot air conduit means longi tudinally of and in spacedrelation to the side walls of said housing toward the receiving endthereof to effectively distribute the warm air more uniformly throughoutsaid hot chamber than would otherwise take place, said hood memberhaving side portions extending at a lower level than its medial portionwhen viewed crosssectionally, and an expeller-type blower mounted in theupper portion of said housing above said conveyor and having an intakeand a discharge communicating with the interior and the exterior of saidhousing respectively whereby hot air and products of combustion will bedrawn and circulated upwardly through said porous conveyor and thestratum of grain thereon and then discharged from the dryer and wherebycool air will be drawn and circulated upwardly through the deliveryportion of said conveyor and circulated in said cooling chamber.

6. A continuous grain dryer having in combination a housing having adelivery end and a receiving end and a top and bottom, an endless porousconveyor extending substantially horizontally throughout the majorportion of the length of said housing and medially disposed relative toaesmsi the height thereof, conduit means in the receiving end of saidhousing adapted when connected to a source of grain to be dried todeliver continuously a stratum of such grain upon the re ceiving end ofsaid conveyor, means for delivering dry grain from the delivery end ofsaid housing to a point exterior thereof, a blast type burner mountedwithin said housing adjacent its delivery end and having a hot airdischarge, a transverse partition dividing the interior of said housinginto a larger hot chamber extending from a point inwardly of said burnerto the receiving end of said housing and a cooling chamber extendingfrom said partition to the delivery end of said housing, said coolingchamber communicating with the exterior at points below said conveyor,said partition having an aperture in the central portion thereof foraccommodating said conveyor and the stratum of grain carried thereby,hot air conduit means receiving from the discharge of said burner anddischarging hot air into said hot chamber of said housing below saidconveyor and directed longitudinally and centrally of said housingtoward the receiving end thereof, said hot air conduit means comprisinga tubular element having a receiving end surrounding the discharge ofsaid burner in spaced relation and a discharge end extending into saidhot chamber, said tubular element being tapered inwardly throughout itslength away from its receiving end whereby increased mixing of the hotair discharged by said burner and the cold air drawn into said elementaround the discharge of said burner may be accomplished prior to itsdischarge into said hot chamber, and an expellertype blower mounted inthe upper portion of said housing above said conveyor and having anintake and a discharge communicating with the interior and the exteriorof said housing respectively whereby hot air and products of combustionwill be drawn and circulated upwardly through said porous conveyor andthe stratum of grain thereon and then discharged from the dryer andwhereby cool air will be drawn and circulated upwardly through thedelivery portion of said conveyor and circulated in said coolingchamber, said tubular element having at least one port formed in itswalls opposite the discharge of said burner to provide increasedcommunication between the interiorof said element and the exterior andto therebyinduce increased mixing of the hot air with the cool air drawninto said tubular element from.

its exterior as a result of the vorticity set up within the interior ofsaid tubular element by the flow of cool air through said port intosaid. element.

BEN L. TOMLINSON. DONALD E. CARLSON.

References Cited in the le 0f this patent UNITED STATES PATENTS NumberName Date 889,560 Thull June 2, 1908 2,369,706 Altamore Feb. 20, 19452,406,822 Fox Sept. 3, 1946y 2,490,176 Tomlinson et al Dec. 6, 19492,518,021 Keay Aug. 8, 1950 2,553,029 Bailey May 15, 1951 FOREIGNPATENTS Number Country Date 905,242 France Nov. 28. 1945

